This invention relates to dental apparatus and more particularly to a rotary table saw which can be used for segmenting sections of dental models.
In various dental procedures, a dental model is initially formed. After the model has been accurately formed, it is often necessary to segment the dental model into sections with each section having the capability of being returned to its original position into a dental tray or base. The segmenting must be done very carefully, in order to avoid damaging the marginal line which will occur where the restoration will join the natural portions of the mouth structure. In order to protect such margin, typically the dental models are cut by hand from their occlusal side.
In the cutting and segmenting of the model, initially a line is identified along which the cut should be made. Then, cutting with a thin blade, the dentist or technician will cut through from the occlusal side as far down as possible. He will then break off the segment after the cut has substantially passed through most of the dentition portion of the model.
Since the cuts are typically made by hand using a thin blade with a handsaw, numerous problems occur introducing inaccuracies in the cutting. For example, the saw may angle or bend along the way and the cut will not be perfectly straight. In fact, sometimes undercuts will occur whereby it will not be possible to replace that segment without further trimming and cutting down of important aspects of the dental model which would otherwise be preserved.
Also, the accuracy and repeatability of the cuts is difficult to achieve by hand.
Where automatic large rotary saws are utilized, dangerous situations may occur and the type of sawing which is achieved frequently causes breakage of the model itself. Typically, a horizontal rotary saw is utilized which rotates towards the operator. The operator holds the model in fixture and then pushes the model in the fixture against the horizontal rotary saw.
Frequently the model may not be such that it can fit into a fixture for the particular segment that is being cut. As a result, the dentist or technician may actually try holding it by hand causing a further dangerous condition. During such operation, the dental model which is held by hand or in a fixture can break. Additionally, the toothed blade utilized in the saw can actually catch the dentist's hand causing a deep cut or gash.
The rotary blade which is utilized also presents a hazard. If the blade is covered and shielded prior to use, then the shield must be lifted as the dental model is brought against the saw. This causes awkwardness since the dental model must be held in only one hand and the shield removed with the other hand. Holding the model with only one hand is dangerous and may cause breakage of the model.
Where the rotary blade is fully exposed, while the model can be held with two hands, the exposed blade presents a hazard prior to its being used.
Prior to the present invention, dental models were segmented generally using a manual operation. Typically, after the dental model is completed, it is desirous to segment the model. Caution must be had to maintain the margin between the natural and artificial parts in a protected state. Accordingly, an initial indication is usually provided on the occlusal side of the teeth protecting the marginal area. A thin blade is then used to saw downward from the occlusal surface to the bottom, usually through all of the dental model and into the base. Either the sawing goes completely through the base, or the bottom is simply broken off.
Where a rotary saw is utilized, such rotary saws are usually of the type that rotate towards the operator. The operator holds the model in a fixture and presses the model against the saw. This is often difficult since the model may not always to of a type or shape that can be maintained in a fixture. As a result, it can fracture the model or the user is forced to hold the model by hand without fixture. This is dangerous, especially when the blade is rotating toward the operator.
Additionally, when such a rotary blade is utilized, it is usually exposed. As a result, when the operator begins, the blade is already rotating and if the operator slips, the blade can cut into his hand.
If a protector were to be placed over such a rotary blade, it would be necessary for the user to lift the protector with one hand, leaving only the other hand for holding the model which is dangerous to hold the model with one hand while trying to saw it.
Accordingly, improvements are warranted in the type of rotary saw which is utilized for segmenting dental models so as to avoid hazards, improve the ability to cut and separate the model into segments, and improve the accuracy, repeatability, and other cutting functions not heretofore achievable with prior art devices.